得到553 5.1.8 ..发件人域不存在错误

我目前正在使用PHP和CodeIgniter框架做一个网站。在用户提交表单之后，我希望自动向管理员和刚刚注册的用户发送一封电子邮件。为了做到这一点，我使用以下代码:

$this->email->initialize(array('mailtype' => 'html', 'charset' => 'utf-8'));
$this->email->to($row[0]['EMAIL']);
$this->email->from('noreply@portail-du-climat.ec.gc.ca', 'Portail du climat');
$this->email->subject('blabla');
$this->email->message('blabla');
$result = $this->email->send();
echo $this->email->print_debugger();
$interestedAdmins = $this->User->getInterestedAdmins($row[0],$this->adminContactList);
$this->email->initialize(array('mailtype' => 'html', 'charset' => 'utf-8'));
$this->email->to($interestedAdmins);
$this->email->from('alerteAutomatique@portail-du-climat.ec.gc.ca');
$this->email->subject('blabla');
$message  = "blabla";
$this->email->message($message);
$result = $this->email->send();
echo $this->email->print_debugger();

不幸的是，通过这样做，我在两个电子邮件发送尝试中得到以下PHP错误:

A PHP Error was encountered
Severity: Warning
Message: mail(): SMTP server response: 553 5.1.8 ... Domain of sender address noreply@portail-du-climat.ec.gc.ca does not exist
Filename: libraries/Email.php
Line Number: 1553

作为参考，这里是Email.php(这是一个来自CodeIgnitor的文件)中的行号1553:

if ( ! mail($this->_recipients, $this->_subject, $this->_finalbody, $this->_header_str, "-f ".$this->clean_email($this->_headers['From'])))

我能做什么来解决这个问题?